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https://issues.apache.org/jira/browse/SPARK-29438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16955798#comment-16955798
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Jungtaek Lim commented on SPARK-29438:
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This would be pretty much easier to reproduce: make left side of union changing
its number of partitions at any chance, then right side of union (stream-stream
join, no need to be outer join) would throw error.
The chance of having number of partitions changed from left side of union is
pretty easy - for example, Kafka streaming source. It doesn't guarantee fixed
number of partitions, which means the number of partitions can be changed
between batches.
It doesn't seem to hit an edge-case - fairly easy to reproduce, so priority of
'critical' seems OK to me, and even I think it should be a 'blocker' as the
query can be crashed at any time.
> Failed to get state store in stream-stream join
> -----------------------------------------------
>
> Key: SPARK-29438
> URL: https://issues.apache.org/jira/browse/SPARK-29438
> Project: Spark
> Issue Type: Bug
> Components: Structured Streaming
> Affects Versions: 2.4.4
> Reporter: Genmao Yu
> Priority: Critical
>
> Now, Spark use the `TaskPartitionId` to determine the StateStore path.
> {code:java}
> TaskPartitionId \
> StateStoreVersion --> StoreProviderId -> StateStore
> StateStoreName /
> {code}
> In spark stages, the task partition id is determined by the number of tasks.
> As we said the StateStore file path depends on the task partition id. So if
> stream-stream join task partition id is changed against last batch, it will
> get wrong StateStore data or fail with non-exist StateStore data. In some
> corner cases, it happened. Following is a sample pseudocode:
> {code:java}
> val df3 = streamDf1.join(streamDf2)
> val df5 = streamDf3.join(batchDf4)
> val df = df3.union(df5)
> df.writeStream...start()
> {code}
> A simplified DAG like this:
> {code:java}
> DataSourceV2Scan Scan Relation DataSourceV2Scan DataSourceV2Scan
> (streamDf3) | (streamDf1) (streamDf2)
> | | | |
> Exchange(200) Exchange(200) Exchange(200) Exchange(200)
> | | | |
> Sort Sort | |
> \ / \ /
> \ / \ /
> SortMergeJoin StreamingSymmetricHashJoin
> \ /
> \ /
> \ /
> Union
> {code}
> Stream-Steam join task Id will start from 200 to 399 as they are in the same
> stage with `SortMergeJoin`. But when there is no new incoming data in
> `streamDf3` in some batch, it will generate a empty LocalRelation, and then
> the SortMergeJoin will be replaced with a BroadcastHashJoin. In this case,
> Stream-Steam join task Id will start from 1 to 200. Finally, it will get
> wrong StateStore path through TaskPartitionId, and failed with error reading
> state store delta file.
> {code:java}
> LocalTableScan Scan Relation DataSourceV2Scan DataSourceV2Scan
> | | | |
> BroadcastExchange | Exchange(200) Exchange(200)
> | | | |
> | | | |
> \ / \ /
> \ / \ /
> BroadcastHashJoin StreamingSymmetricHashJoin
> \ /
> \ /
> \ /
> Union
> {code}
> In my job, I closed the auto BroadcastJoin feature (set
> spark.sql.autoBroadcastJoinThreshold=-1) to walk around this bug. We should
> make the StateStore path determinate but not depends on TaskPartitionId.
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